Centralized traffic control system for railroads for the code control of interlocked track switches and signals



Sept. l1, 1951 E. M. ALLEN 2,567,834 OENTRALIZED TRAFFIC CONTROL sys-TEM FOR RAILROADS FOR THE CODE CONTROL OF INTERLOCKED TRACK SWITCHES AND SIGNALS Filed June l1 1945 4 Sheets-Sheet 1 fl I R/ 43E @IMF @ma @mi 15W 256 3.5- 456' Nw? z3/5? NW2 812 @9.14. 25mg 26'@ Q46@ 114 IN1/avra@ Sept. 11, 1951 E. M. ALLEN 2,557,834

lCENTELALIZIEJD TRAFFIC CONTROL SXSTEMVFOR RAILROADS FOR THE CODE .CONTROL OF -INTERLOCKED TRACK'SWITCHES AND SICNALS Filed June 11 1945 4 Sheets-Sheet 2 l 15' mi? dj HIS ATTORNEY Sept. 11, 1951 E, M ALLEN 2,567,834

CENTRALIZED TRAFFIC CONTROL SYSTEM F OR RAILROADS FOR THE Y CODECONTROL OF' INTERLOCKED TRACK SWITCHES AND SIGNALS Filed`June ll 1945 4 Sheets-Sheet 5 431m LFO@ g L Z'MS, ZLAR Zrm 4R45 5773i a g 7 PVWP []17 I eus 23491713 41245' 4R45' 571A LA? al Z4.

.,1 INVENTOR.

Y l j 4005, 7a3/Iz( M14/(STIL a: I @im *H3* [Wg 25 f Hg ITA? e b b' M 2&4@ m :DEU @QW/agr Sept. l1, 195i y E, CENTRALIZED TRAFFIC CONTROL INTERLOCKED CODE CONTROL OF Filed June 2,557,834 SYSTEM FOR RAILROADS FOR THE TRACK SWITCHES AND SIGNALS M. ALLEN @ifm L@ 494621966 45H5' ZIEH A41u15' 4m 5m V f 419,457 4019 V 1 E E@ fg; 2z?.

A INVENTOR.

HIS' ATTORNEY 4to Vprovide a control PatentedY Sept. 11, 1951 UNITED STATES PATENT OFFICE oENTRALIzE-D TRAFFIC `CONTROL lSYSTEM FoRRaILRoADs Fon TIInCoDE CONTROL F INTEaLoCKED mack SWITCHES AND SIGNALS Earl Allen, Swissvale, Pa., assignor to The 4Union Switch & `Signal -Company,

.Swissvale,

Pai, a corporation of gPennsylvania Application June 11, 194 5, Serial No. 598,695

7 .Claims 'My invention relates to centralized ltraic control systems for railways, and more particularly 'to railway trailic controlling apparatus 4for the taining red vlamps lwhich are lighted -to indicate train movements `throughthe various track sections. Heretofore the usual practice has/been to also provide a group of lamps for each switch -or Vsignal lever, one lamp of each group being nor- Ymally lighted to indicate the position ofthe switch or the condition of the signal controlled by the associated lever. If the plant'is a large one this involves the continuous display of such a large number Yof lights as to tend Vto confuse -the operator, requiring careful observation in order lto correctly set up the diierent routes.

AOne object of my invention is the provision of an improved control board for a system of this character, -in-which all of the lever'lamps as -well as those/for illuminating the track diagram are -normally dark. vThe Ymanipulations involved in setting up routes are thereby facilitated, because the only lamps vlighted at any one time are those which are directly-of interest -to the'operator. In the embodiment of my invention disclosed herein I rprovide a single red lamp for each-lever, which becomes lighted when the lever is moved to anew position, and which becomes Adark again whenA the switch or signal which the lever controls assumes a corresponding position. vInaccordance withone feature of my vinvention I provide a lamp on the track diagram-for` the exit end of each route by means of which a-directional indicator orl arrow is illuminated tomar-k the destination of each established route, and I .also provide a green lamp at each signal location on the track diagram which is lighted when the ycorresponding signal is cleared. with this plan, when the operator reverses a signal .lever for clearing a signal governingtraffic movements over a selected route, a.red `lamp above the lever becomes lighted, A.and when a route governed kby such signal is established which corresponds :with the positions of the switch leversthe lamps associatedwith these switchlevers become dark, and on the track diagram, the corresponding Aexit f lamp becomes lightedtherebyf distinctively indicating. the. :des-

In accordance 2 tination of the selected route bythe lighting yof only one lamp. Furthermore, in order tov permit the operator to Verify the selection before-the vsignal is cleared, the operations for rclearing Vthe signal are divided into two steps. The operator Ifirst reverses the signal lever for the signal at the entrance end of the route and Lthen, after kverifying -the destination as indicatedby `the exit lamp, presses a startingvbutton associated with the lever to effect the clearing of the signal. When the signal clears, the red-lamp associated with the lever is extinguished'and a green lamp on the track diagram at the signal-location becomes lighted.

l'In the yform shown herein, the apparatus of my invention is so arranged that all communication between the control oflice and the plant location is effected over a single pair of line wires, employing a selective code system such as -tha-t shown inLetters Patent of the United'States'No. 2,229,249, issued January 21, 1941, tollloyd V. Lewis for Remote Control'Systems.

I shall now describe one form of apparatus `embodying my invention and shall then point out y` the novel features thereof in claims.

Referring to the accompanying drawings, Figs. 1A to 1E, inclusive, taken together show the circuits andy apparatus located at the o iiceforone form of my invention asY applied to a typical track layout, while Figs. 2A to 2D, inclusive, yshow the 'corresponding wayside apparatus at the `plant location.

For simplicity, a layout of a minimum szelhas been chosen to illustrate the invention, and as shown by the track plan in Fig. 2A,vthis comprises a track section IT containing a single switch I and extending between theopposing signalsgZRA or ZRB and 2LA or-2LC. which sec- ;tion is connected by a crossover Y3 with a section ;3Tlocated in a parallel track and extending between the opposing signals v1R-A or 4R0 and 4L.

Considering lthe drawings in detail, fFig. l 1A shows the operators control board, which includes an illuminated track diagram of the llayout mounted above a l panel containing the usual switch and signal control levers, ywhile.Fig. 1B shows the -circuits for the Ltrackdiagram-lamps. Fig. 1C shows the oiice indication .relaysffor controlling the. circuits of VFig..1B, which-relays .are controlled by indicationv codes. transmittedin .response to changes in the condition..ofthe,.con trolling. relays in the vfield. In vorder-to make. it :unnecessary rto consider herein the .details `of Voperation of the codesystem, the Various intermit- ,tently available indication channels which itl provides are represented, as individual Wires, numbered |09 to H5, inclusive, to correspond with the wires of Patent No. 2,229,249, over which the code impulses are supplied to the relays whenever a delivery relay such as relay 2D or 4D is momentarily energized. For simplicity these wires are indicated herein as extending directly to the contacts of the controlling relays of Figs. 2A to 2D. The indication relays as shown differ from those of the remote control system of the Lewis patent hereinbefore referred to, and correspond to those employed in a modification of that system which is particularly adapted for use in connection with -the apparatus of my invention and which is shown in Letters Patent of the United States No. 2,442,603, issued June 1, 1948, to A. P. Jackel. In this arrangement but one signal indication relay such as' relay `2GK is provided for indicating the clearing of any one of the confiicting or opposing signals of the group of signals identified by the same number, and a second relay such as relay ZASK is provided to indicate the transmission of a control code for clearing any o the signals of the corresponding group and to also indicate the release of any of the approach locking relays associated with such group of signals.

Fig. 1D shows a route circuit network for controlling route relays such as the relay ZRGS of which one is provided for each of the two reverse positions of the associated signal lever such as the lever ZSG, the route circuits for these relays including contacts of the switch levers such as lever ISW and of the switch indication relays' and conforming to the various routes. Each route relay such as the relay 2RGS controls the circuit in Fig. 1B for a green lamp ERBE or ZRAE for the corresponding signal and for the exit lamp ZLX or GLX at the opposite end of the established route, and in Fig. 1C, locally controls the associated lock indication relay ZASK.

Fig. 1E shows the circuits for the lever lamps and for governing the transmission of the controlv codes by which the switches and signalsare controlled in accordance with the positions of the control levers. For an understanding of my invention itl is Vdeemed sufficient to point out that a control code is initiated by energizing a starting relay such as the relay IST or 3ST which governs the transmission of a group of code elements for selecting' the group of devices in the iield'which the associated levers controls and also energizes a selector relay IS or 3S by means of which one or more of a group of wires IUI- |05 corresponding to the similarly numbered'control code channels of Patent No. 2,229,249 are energized in accordance with the positions of the y levers. As shown herein, the circuits of the patent are modified in two particulars; first, the circuits for energizing Wire |92 or |04 by reversal of a signal lever such as ZSG include contacts of the associated route relays of Fig. 1D, so that a code including elements for clearing a signal cannot be transmitted until the route governed `momentarily energizedyalong with relay IS or n by the signal is established and the route relay I is energized, and second, the switch levers such as lever ISW are made of the push-turn type and are provided with an auxiliary contact a which is closed to energize the associated starting relay whenever the lever is rotated from one of its two operating positions to the other, but without operating the usual-starting button such as the button ZSTB by which a code is initiated following an operation of the signal lever ZSG.

Fig. 2A in addition to the track plan shows the circuits for the track relays TR, for the aptrolled switch shows the circuits for the code .con-

and signal control relays NWS, RWS, LHS, RHS and COS, which correspond to those of Patent No. 2,229,249 except that for simplicity the circuits are represented as providing direct connections over wires IDI- |05 to those of Fig. 1E when adelivery relay ID or 3D is 3S, in response to a control code.

Fig. 2C shows the signal circuits, comprising a circuit network conforming to the track layout, for controlling the mechanisms for the various signals shown in Fig. 2A. Each mechanism is identified by the reference character G preceded by the designation for the corresponding signal as shown in the track plan, it being understood that these are of the well-known searchlight type.v

Each signal mechanism comprises a normally lighted lamp and a winding which when energized. opens a contact, shown in Fig. 2D, and also operates a spectacle frameA for placing different colored roundels in front of the lamp. Each signal is adapted to display a red or stop aspect when deenergized, to display a yellow or caution aspect when energized, provided terminalB is connected to the right-hand terminal of its winding and to display a green or proceed aspect.

gizedl when the next signal in advance for the same direction, not shown herein, indicates caution or proceed.

Fig. 2D shows the circuits for approach locking relays LAS and RAS which are controlled by the signals and by their control relaysfin the conventional manner. These relays control the switch locking relays LR of Fig. 2A, which relays must be energized to permit operation of the track switches, and as shown by Fig. 2C, the approach locking relay LAS or RAS for a signal that is to be cleared as well as the switch locking relays LR controlled thereby must occupy their deenergized positions in order to ypermit the sigynal to be cleared. As shown in Fig. 2D, the aplatter by the route relay RGS or LCrS` of Fig. 1D

is such as to insure that the switches of a route being set up will not become locked until all have assumed the required positions.

Similar reference characters refer 'to similar parts in' each of the several views.

To simplify the circuits. I have herein shown only the-terminals of the sources of current for energizing the relays, the reference character B designating the positive or supply terminal and the reference character C the negative of common return terminal of the local sources of current lat the office and eld location, respectively.

The operation of the system of my invention will now/:be described under different assumed conditions, starting with the apparatus in its normalconditionas shown, in which all of the indication lamps in Fig. 1A are dark, vand assuming first that the operator desires to set up the route which includes switch I reversed and crossover 3 reversed and to clear signal v2RB-for a movement from left to right over that route.

The operator rst moves levers ISW and SSW to their reverse or right-hand positions, thereby closing the lever contacts ain Fig; 1E momentarily to pick up relays IST and SST, and lighting the lamps IWE and SWE. over the circuits including the switch lever contacts b and back contacts f of the reverse indication relays IRWK and SRWK.

The circuits for the route relays of Fig. 1D are now open. The circuit from contact b of lever ZSG to contact c of the same lever is open at contact d of lever ISW and at contactd of lever SSW; the circuit from contact b of lever ISG to contact c of the same lever is open atcontact e of lever SSW, and the circuit from contact b of lever ZSG to contact c of lever IISG is open at contact e of relay IRWK and also at contact c of relay SRVVK, consequently these route relays are released yand wires |02 or |04 are not energized, and the two control `codes which are now transmitted in response to the operation of the starting relays ISTiand 3ST include no elements for clearing any signal. Wire Y|03 is energized over the reverse contact a of lever ISW or SSW, so that in Fig. 2B the switch control relay IRWS becomes energized and relay INWS releases in response to the first control code, and relay SRWS is energized and relay SNWS released in response to the second, thereby reversing the switch operating relays IWR and SWR, Fig. 2A, to release the switch normal indicating relays INWP and SNWP and to supply energy to the switch machines ISM, SSM and SASM to operatev the track switches to reverse. The release of relays INWP and SNWP initiates the transmission of indication codes in the usual manner, whereby relays INWK and SNWK are released, which prevents the extinguishing of lamp I'WE or SWEi or the reestablishment of the original route circuits in case the operator should inadvertently'restore lever ISW or lever SSW to its former position.

When the track switches become lockedk reverse, relays I RWP and SRWP become energized and initiate the transmission of indication codes whereby relays IRWK and SRWK are energized to extinguish lamps I-WE and SWE, and to prepare a route circuit in Fig. 1D' over theclosed contacts of the switch levers. Noting that the switch lever lamps have becomeA dark, theoper- `atorv moves lever 2SG to its right-hand reverse position, completing a pick-up circuit for the route relay ZRGS. This circuit Fig. 1D from terminal B at vback contact b Aof relay ALGS over the normal contact c of lever dSG, the reverse contact e of lever SSW, contact c of relay SRWK, contact e of relay IRWK, theA reverse contact d of lever ISW, the right-hand' contact b of lever 2SG, back contact b of relays I-ST and QASK through relay ZRGS to terminal C. In response to the operation` of lever ZSG, lamp ZNE becomes lighted, its circuit Aas shown in Fig. 1E` extending from terminal B at back contact e of relay ZASK, back contactl f of relay ERC-S and the right-hand contact d of lever ZSG through lamp ZNE to terminal C; Relay ZRGS now assumes its energized positiony and its contact j shifts the circuit for lamp ZNEy to the branch which extends to tact c of relay ZGK. Theexitlamp.411Ky becomes lighted', its circuit,

may be traced in terminal B at back conshcwnl innig; 1B, extending' :aggregaat After observing the lighting of lamps ZN and.

ALX, andt-hcreby checking that the desired route is established, the operator presses the starting button -ZSTB momentarily to energize the starting relay IST. In Fig. 1D, contact b of relay IST shifts to its' upper position and thereby inserts contact a of relay ZRGS into the route circuit over which rela-y 2RGS is energized. It follows that relay ZRGS must assume its energized position prior to thel operation of relay IST, and cannot become energized while a code is in progress with relay IST energized, for example. The energization of relay I ST,.following that of relay ZRGS, initiates the transmission of a control code, during which relays IS and ID pick up toeffect the energization of wire |04, over Contact b of relay-IS, right-hand contact a of |03 is also energized as in and relay IRWS is held energized. The energization of relay IS also completes a circuit in Fig.. IIC from terminal B at a contactc of the code: system relay OM, which contact is closed only during the transmission of a control code, over' contacts e of relays ZRGS and IS and a back contact of relay 2D through the winding ofthe lock indication relay ZASK to terminal C, sothat relay ZASK picks up and completes a stick circuit at its own front Contact a and in 1D, contact b of relay ZASK shifts to its upper position to disconnect relay'ZRGS from the route circuit and to hold it energized over a stick circuit including its own front contact b.` The transmission of a control code for clearing the signal tlius'locks relay ZRGS energized and thereby prevents the energization of the route relays for opposing or conflicting routes, the circuits for which include its back contact b.

When the signal 'control relay ZRHS becomes energized in response to this code, its back contact e opens lin Fig. 2D and releases the approach locking relay ZRAS, and in Fig. 2A, Contact c of relay 2RAS opens, releasing the switch locking relays ILR and SLR, and the latter relays then open their contacts a and b to isolate the switch contro-l relays I WR. and SWR and thereby lock the track switches in the positions required for the route, and also open their contacts e, f and g, in Fig. 2B, to prevent a change in the positions of' the switch control relays as lon-g as the switches remain locked.

In Fig. 2C, a circuit for the signal mechanism. ZRBG which corresponds to the established' route has been prepared by the closing of contacts a and b of relay IRWP, contact a of relay SRWP, contacts c and d of relay ZRHS, and the back contact d of relay ERAS. This circuit extends to terminal B at front contact d' of relay 4LAS and is completed by the closing of back contacts c of relays ILR and SLR, so that mechanisrn ZRBG becomes energized to clear signal.l ZRB of Fig. 2A.

The release of relay 2RA'S and the consequent energization of mechanism ZRBG as described results in the initiation of an indication code,.

2D, Fig. 1C to be momentarily energized, completing circuits over wires II`2` and' H5 to Vholdv the indication relays' ZASK and' IRWK'er-i'ergized; and also completing 'a circuit' 7 controlled byfcontact a of `mechanis'in-` ZRBG `including wire IIII to cause-the signal indication relay ZGK to become energized. j

In Fig. 1E, the red lamp 2NE is extinguished by the opening of back contact c of relay ZGK and the green lamp ZRBE in the track diagram becomes lighted due to the closingof its circuit in Fig. 1B which extends from terminal B at contact b of relay ZGK over contacts dof relays 2RGS and IRWK through lamp-2RBE to terminal C. f

The established route is thus indicatedV on the track diagram by the lighting of the, green lamp ZRBE at one end and bythe exit `lamplIlX at the other end, all other indicationY lamps being dark. Y f

I shall now assume that a train governedby signal ZRB passes through section IT. The track relay ITR will release, initiating an indication code by which relay ITK, Fig. 1C, is energized. closing a circuit in Fig. 1B to light a red lamp ITE in the track diagram. Theoperator will then restore lever ZSG to its normal ycenter po@ sition and press the starting button ZS'IB, thereby initiating a control code which releases relay ZRHS, thereby deenergizing mechanism ZRBG and restoring signal ZRB to stop. The red lamp 2NE becomes lighted over the center contact d of leyer2SG and the front contact'd of relay 201K,A lamps ZRBE and 4LX in the track diagram remaining lighted. If this control code is received while section IT is occupied, relay ZRAS, Fig. 2D, becomes reenergized over the circuit including back contacta of relay ITR, and the resulting indication coder will cause relays ZGK and 2ASK to release. Relay ZASK will release relay ZRGS and lamps ZNE, 2RBE and IILX will be extinguished. On the other hand, if signal ZRB is put to stop by a control code received while section IT is not occupied, relay 2RAS will remain released, and an indication code will be initiated by the release of mechanism ZRBG by which relay 2GK is released. relays ZASVK'and ZRGS remaining energized. Lamp v2RBE will be extinguished, lamp 4LX will remain lighted, and lamp 2NE will display a flashing indication, being energized intermittently over back contact d 'of relay ZGK and front contact d of relay ZASK from one terminal FB of a suitable source of interrupted current. In Fig. 2D, the release of relay ZRHS when section IT is'unoccu'pied com-4 pletes Ya circuit over back contact a of relay ZRAS and front contact d of relay ITRor a time element relay ITER, which relay becomes ener" gized and opens its checking contact c in the sig*- nal circuits of Fig. 2C and after a suitable time interval completes a circuit at itsY contact a, in Fig. 2D, to reenergize relay ZRAS, whereupon an indication code is initiated whereby relays ZASK and ZRGS are released in turn, and lamps :NE and 4LX are extinguished. It will be seen therefore that the ashing of lamp ZNE provides a distinctive indication which pervsistsas long as the time locking by relays ITER and' 2RAS is effective. This flashing indication also displayed automatically under the condition that` the signals controlled by lever 2SGhave not been cleared, in the event that relay 2RAS or ZLAS releases due to a fault, relay ZASK be-` coming energized and completing a flashing cir?V cuit for lamp INE over back contact j of relay ZLGS or 2RGS and front contact e of relay or over back contact d of relay ZGK and iront contact Vd of relay ZASIS wherebyla'rrpJ 2KB t0 Signal caused to flash irrespecI-,iyc of the position of le-'- ver ISG.; Y Y Y I shall now assume, that the route from signal 4L -is set up as above described, with relays 2ASK and ZRGS released and the indication lamps dark, and that the operator moves lever IISG to its left-hand reverse position to clearY signal 4L. The operations occurring as the result of pressing the starting button AS'IB in this case are analogous to those already described, the principal difference being in the switch locking. Since relay 4LAS may be reenergized as soon as a train passes signal 4L and occupies the first section 3T of the route, and since relay ITR does not release until the train enters the second section IT of the route, neither of these relays is adapted to lock switch I when a train insectionfST is approaching section IT. To maintain switch I locked under this condition a section lookin grelay IWS is provided, the operation of which will be self evident from the circuits as shown in Fig. 2A.

I shall next assume that the apparatus has been restored to the condition shown, with switches I and 3 normal, and that the operator wishes to clear the high signal LA'for a train movement over the upper main track. The operator will first move lever 2SG to the left, lighting lamp ZNE. The route relay ZLGS becomes energized at once over the route circuit already established, lighting lamp ZRAE., whereupon the operator pressesbutton ZSTB to energize the starting relay IST and initiate the transmission of a control code by which relay ZASK, inlig.V 1C. is energized over contact e of relay ZLGS, and relay ZLHS. in Fig. 2B, is energized over wire |02. Relays ZLAS, ILR and 3LR. release to lock the track switches and to complete a circuit for mechanism ZLAG to clear signal 2LA, following which an indication code is transmitted to energize relay 2GK and thereby extinguish lamp ZNE and to light lamp 2LE in the track diagram. The approach of a train is indicated by the lighting of lamp ZAE, and when the train passes signal 2LA at clear, mechanism ZLAG is released to put the Asignal automatically to stop by the opening of contact c of the track relay I'IR in its circuit, and at the same time relay ZLHS, Fig. 2B, is released bythe opening of contact f of relay ITR, and relay"2LAS, in Fig. 2D, is reenergized automatically over the circuit including back contact b of relay ITR. The indicationcode which is initiated in this case causes relay ITK to become energized to light lamp ITE, and relays ZGK and ZASK to release, thereby releasing relay ZLGS and causing lamps ZLE and ZRAX to become dark, andv lamp ZNE becomes steadily lighted over the left-hand contact d of lever ZSG, back contact f of relay 2LGS and back contact e of relay ZASK, becoming dark when lever ZSG is returned to its normal center position to correspond with the conditionof the signal, the transmission of a stop signal control code not being required in this instance.

In the event signal 2LA is restored manually to stop With the approach section 2LT unoccupied so that the approach relay ZLAR, Fig. 2A, is energized, relay ZLAS becomes energized at once in response to the release of relay ZLHS and mechanism ZLAG, over front contact b of relay ZLAR, but if the4 approach sectiotn 2LT is occupied atfthe time, relay ZLAS is reenergized only after the time interval imposed by relay ITER.

.It willy be vnoted that the approach relay ZLAR 7l a Stickrelay which can be picked up only when the front contact b of relay ZLAS is closed. This arrangement insures that if signal'ZLA is put to stop when an approaching train occupies section 2LT, relay ZRAR will be held releasedvby relay ZRAS, and consequently relay ZLAS remains released to maintain the switch `locking eiective even though the track relay ZL'I'R is temporarily energized due to ineiective shunting of the track rails by the approaching train.

Associated with the high speed signal ZLA or 4RA, a slow speed or call on signal 2LC or 4R0 is provided, which may be controlled in the manner described in Patent No` 2,229,249 by relay ZCOS or COS in response to the operation of a key 2CO or 4CO associated with the signal lever.

It will be understood that the several control codes which are transmitted when a plurality of starting relays ST are operated, are transmitted in a prescribed order of code superiority. The operation of the apparatus of my invention is such that if any of the codes of a group includes elements effective to change the position of a track switch none of these codes will include an element for clearing a signal governing movements over that switch, due to the release of the route relays of Fig. 1D by switch lever operation. On the other hand, if a code for clearing a signal is transmitted first, the resultant locking of the switches is anticipated by the locking of the route relay in its energized position as soon as the code is transmitted, and one effect of this code is to release certain locking relays whereby codes transmitted subsequently .are rendered incapable of changing the positions of the switch control relays.

Although I have herein shown and described only one form of apparatus embodying my invention, it will be understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a centralized traffic control system for railroads, a track layout including track switches and signals for governing traffic movements over the different routes in said layout, a miniature track diagram of said layout at a control office, switch levers for controlling said switches, route relays for governing said signals, signal levers for controlling said route relays to effect the clearing of said signals, switch indication relays which reect the positions of said switches and signal indication relays which reflect the condition of said signals, a route circuit network including a circuit for each route relay closed when the associated signal lever is reversed but only ii said switch indication relays indicate that a route corresponding to the positions of said switch levers is set up which has its entrance end at the location of the signal which such route relay governs, a signal lamp at each signal location in said track diagram, an exit lamp at the exit end of each route in said track diagram, a circuit for each exit lamp prepared by said switch indication relays when a route having the corresponding exit end is set up and completed upon the energization of the route relay for the signal at entrance end of such route over the corresponding circuit in said network, and a circuit ici' the signal lamp for said signal prepared by said route relay and completed by the corresponding signal indication relay when said signal clears.

2. In a centralized traic control system for railroads, a track layout including track switches and signals for governing trac movements over the different routes in said layout, a miniature track diagram of said layout at a control office, switch levers for controlling said switches, route relays for governing said signals, signal levers1 for controlling said route relays to effect the clearing of said signals, switch indication relays which reflect the positions of said switches, signal indication relays which reflect the condition of said signals, a route circuit network including a circuit for each route relay closed when the associated signal lever is reversed but only if said switch indication relays indicate that a route corresponding to the positions oi said switch levers is set up which has its entrance end at the location of the signal which such route relay governs, a signal lamp at each signal location in said track diagram, an exit lamp at the exit end of each route in said track diagram, a circuit for each exit lamp prepared by said switch indication relays when a route having the corresponding exit end is set up and completed upon 'the energization of the route relay for the signal at the entrance end of such route over the corresponding circuit in said network, a/push button associated with each signal lever, a-signal control relay for each signal, means responsive to the operation of each push button having its associated signal lever reversed for operating the signal control relay for the associated signal, the operation of such signal control relay being also dependent upon .the energization of the associated route relay as manifested by the lighting of an exit lamp on said track diagram, locking means controile'd by each energized route relay in response to the operation of the associated push button for maintaining such route relay energized as long as the associated signal lever is reversed irrespective of the condition of the circuit in said network over which such route relay was initially energized, means for clearing each signal in response to the energization of the corresponding signal control relay, and means controlled by the signal indication relay for the signal that is cleared and by the energized route relay for` selectively lighting the signal lamp on the track diagram which corresponds to the signal that is cleared whereby the route set up is indicated by the lighting of a signal lampy at one end and of an exit lamp at the other end of its representation on the track diagram.

3. In a centralized traino control system for railroads, a track layout including track switches and signals for governing traic movements over the diierent routes in said layout, a miniature track diagram of said layout at a control office, switch levers for controlling said switches, route relays for governing said signals, signal levers for controlling said route relays to eiect the clearin'g of said signals, switch indication relays which reect the positions of said switches, a route circuit network including a circuit for each route Arelay closed when the associated signal lever is reversed but only if said switch indication relays indicate that a route corresponding to the positions of said switch levers is set up which has its entrance end at the location of the signal which such route relay governs, an exit lamp at the exit end of each route in said track diagram, a circuit for each exit lamp closed only when the route relay for a signal at the opposite end of the `layout from the location designated by such exit lamps is energized over a circuit in said network completed by said switch indication relays which indicates that a route is set up from the location of such signal to the location designated by said exit lamp, whereby the establishment of each route is indicated by the lighting of a lamp which also indicates its destination on said track diagram, and a circuit for clearing each signal including a normally open manually controllable contact and a reverse contact of its signal lever and also including a contact closed in response to the energization of its route relay as manifested by the lighting of the corresponding exit lamp, whereby the destination of such route may be verified before the signal is cleared, by observation of said exit lamp.

4. In a centralized traffic control system for railroads, a track layout including track switchesy and signals for governing traffic movements over the different routes in said layout,y a miniaturek track diagram of said layout at a control office, switch levers for controlling said switches, route relays for governing said signals, signal levers for controlling said route relays to effect the clearing of said signals, switch indication V4relays which reflect the positions' of said switches, a route circuit network including a'circuit for each route relay closed when the associated signal lever is reversed but only if said switch indication relays indicate that a route corresponding to the positions of said switch levers is set up which has its entrance end at the location of the signal which such route relay governs, an exit lamp at the exit end of each route in said track diagram, a circuit for each exit lamp closed only when the route relay for a signal at the opposite end of the layout from the location designated by such exit lamp is energized over a circuit in said network completed by said switch indication relays which indicates that a route is set up from the location of such signal to the location designated by said exit lamp, and auxiliary manually operable means associated with each signal lever for effecting the clearing of the signal which the route relay associated with said lever controls, so arranged that the clearing of any signal in responseV to the energization of its route relay is prevented unless said auxiliary means is manually operated after the destination of the route which such signal governs has been indicated on the track diagram by the lighting of the corresponding exitl lamp.

5. In a centralized traffic control system for railroads, a track layout including track switches and signals for governing traffic movements over the different routes in said layout, a miniature track diagram of said layout at a control office,v

switch levers for controlling said switches, route relays forrgoverning said signals, signal levers for controlling said route relays to effect the clearing oi.r said signals, switch indication relays which reflect the positions of said switches, a route circuit network including a circuit for each route relay closed when the associated signal lever is reversed but only if said switch indication relays indicate that a route corresponding to the positions of said switch levers is set up which has its entrance end at the location of the signal which such route relay governs, an exit lamp at the exit end of each route in said track diagram, a circuit for each exit lamp closed only when the route relay for a signal at the opposite end of the layout from the location designated by such exitk lamp is energized over a circuit in said network completed by said switch indication relays which indicates that a route is set 11p-from the location of such signal to the location desig-A nated by said exit lamp, a push button associated witheach signal lever, signal clearing means responsive to the operation of each push button having its associated signal lever reversed for clearing ther associated signal, said signal clearing means being effective to clear its signal only if operated at a time when the associated route relay is energized as manifested by the lighting of the exit lamp for a route governed by such signal.

6. In combination with a railway track layout including a power operated track switch, a signal for governing traffic movements over a route which includes the switch, a signal lever operable between normal and reverse positions for'controlling said signal, a route relay which is energized in response to the reversal of said lever provided the track switch occupies the position required for said route, a circuit for clearing said signal including a contact closed by the route relay in its energized position and av contact closed by said lever in its reverse position, an indication relay controlled by vsaid signal, an indication lamp associated with said lever, Aa first circuit for energizing said indication lamp including a contact closed by said indication relay when the signal is cleared and a contact closed by said signal lever in its normal position, a second circuit for energizing said indicaiton lamp including a contact closed by said indication relay when the signal is at stop, and a contact closed by the signal lever in its lreverse position, said second circuit also including a contact closed by the route relay in its energized position, and a third circuit for energizing said indication including said contact closed by the signal lever in its reverse position and a contact closed by said route relay in its released position.

7. In a centralized traffic control system for railroads, a track layout including track switches and signals for governing traffic movements over the different routes in said layout, a track diagram representing said track layout having an exit lamp thereon for the exit end of each route, route relays yfor controlling said signals in accordance with the positions of the track switches, indication relays controlled by the track switches, a circuit network including a circuit conforming to each route throughthe track layout including contact of a route relay at one end of said net-' work and from the other terminal of said source through said lamp toa back contact of a route relay at the other end of said network.

EARL M. ALLEN.

REFERENCESy CITED The follow-ing references are of record in the le of this patent:

UNITED STATES PATENTS 

